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Microphotonics is a branch of technology that deals with directing light on a microscopic scale and is used in optical networking. Particularly, it refers to the branch of technology that deals with wafer-level integrated devices and systems that emit, transmit, detect, and process light along with other forms of radiant energy with photon as the quantum unit.
Microphotonics employs at least two different materials with a large differential index of refraction to squeeze the light down to a small size. Generally speaking, virtually all of microphotonics relies on Fresnel reflection to guide the light. If the photons reside mainly in the higher index material, the confinement is due to total internal reflection. If the confinement is due many distributed Fresnel reflections, the device is termed a photonic crystal. There are many different types of geometries used in microphotonics including optical waveguides, optical microcavities, and Arrayed waveguide gratings.
Photonic crystals are non-conducting materials that reflect various wavelengths of light almost perfectly. Such a crystal can be referred to as a perfect mirror. Other devices employed in microphotonics include micromirrors and photonic wire waveguides. These tools are used to "mold the flow of light", a famous phrase for describing the goal of microphotonics. The crystals serve as structures that allow the manipulation, confinement, and control of light in one, two, or three dimensions of space.
An optical microdisk, optical microtoroid, or optical microsphere uses internal reflection in a circular geometry to hold on to the photons. This type of circularly symmetric optical resonance is called a Whispering gallery mode, after Lord Rayleigh coined the term.
Microphotonics has biological applications and these can be demonstrated in the case of the "biophotonic chips", which are developed to increase efficiency in terms of "photonic yield" or the collected luminescent signal emitted by fluorescent markers used in biological chips.
Currently, microphotonics technology is also being developed to replace electronics devices and bio-compatible intracellular devices.For instance, the long-standing goal of an all-optical router would eliminate electronic bottlenecks, speeding up the network. Perfect mirrors are being developed for use in fiber optic cables.
A laser diode, (LD), injection laser diode (ILD), or diode laser is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction. Laser diodes can directly convert electrical energy into light. Driven by voltage, the doped p-n-transition allows for recombination of an electron with a hole. Due to the drop of the electron from a higher energy level to a lower one, radiation, in the form of an emitted photon is generated. This is spontaneous emission. Stimulated emission can be produced when the process is continued and further generate light with the same phase, coherence and wavelength.
Photonics is the physical science of light (photon) generation, detection, and manipulation through emission, transmission, modulation, signal processing, switching, amplification, and sensing. Though covering all light's technical applications over the whole spectrum, most photonic applications are in the range of visible and near-infrared light. The term photonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s.
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
A photonic crystal is a periodic optical nanostructure that affects the motion of photons in much the same way that ionic lattices affect electrons in solids. Photonic crystals occur in nature in the form of structural coloration and animal reflectors, and, in different forms, promise to be useful in a range of applications.
The term biophotonics denotes a combination of biology and photonics, with photonics being the science and technology of generation, manipulation, and detection of photons, quantum units of light. Photonics is related to electronics and photons. Photons play a central role in information technologies, such as fiber optics, the way electrons do in electronics.
Photonic-crystal fiber (PCF) is a class of optical fiber based on the properties of photonic crystals. It was first explored in 1996 at University of Bath, UK. Because of its ability to confine light in hollow cores or with confinement characteristics not possible in conventional optical fiber, PCF is now finding applications in fiber-optic communications, fiber lasers, nonlinear devices, high-power transmission, highly sensitive gas sensors, and other areas. More specific categories of PCF include photonic-bandgap fiber, holey fiber, hole-assisted fiber, and Bragg fiber. Photonic crystal fibers may be considered a subgroup of a more general class of microstructured optical fibers, where light is guided by structural modifications, and not only by refractive index differences.
In optics, an anti-resonant reflecting optical waveguide (ARROW) is a waveguide that uses the principle of thin-film interference to guide light with low loss. It is formed from an anti-resonant Fabry–Pérot reflector. The optical mode is leaky, but relatively low-loss propagation can be achieved by making the Fabry–Pérot reflector of sufficiently high quality or small size.
An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber and transparent dielectric waveguides made of plastic and glass.
A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple photonic functions and as such is similar to an electronic integrated circuit. The major difference between the two is that a photonic integrated circuit provides functions for information signals imposed on optical wavelengths typically in the visible spectrum or near infrared 850 nm-1650 nm.
A hybrid silicon laser is a semiconductor laser fabricated from both silicon and group III-V semiconductor materials. The hybrid silicon laser was developed to address the lack of a silicon laser to enable fabrication of low-cost, mass-producible silicon optical devices. The hybrid approach takes advantage of the light-emitting properties of III-V semiconductor materials combined with the process maturity of silicon to fabricate electrically driven lasers on a silicon wafer that can be integrated with other silicon photonic devices.
Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. The silicon is usually patterned with sub-micrometre precision, into microphotonic components. These operate in the infrared, most commonly at the 1.55 micrometre wavelength used by most fiber optic telecommunication systems. The silicon typically lies on top of a layer of silica in what is known as silicon on insulator (SOI).
The Centre for Ultrahigh bandwidth Devices for Optical Systems is a collaboration of Australian and international researchers in optical science and photonics technology. CUDOS is an Australian Research Council Centre of Excellence and was formally launched in 2003.
A slot-waveguide is an optical waveguide that guides strongly confined light in a subwavelength-scale low refractive index region by total internal reflection.
Microstructured optical fibers (MOF) are optical fiber waveguides where guiding is obtained through manipulation of waveguide structure rather than its index of refraction.
In physics, a high contrast grating is a single layer near-wavelength grating physical structure where the grating material has a large contrast in index of refraction with its surroundings. The term near-wavelength refers to the grating period, which has a value between one optical wavelength in the grating material and that in its surrounding materials.
Plasmonics is the study of plasmons, quasiparticles of plasma oscillation in solids such as metals, semi-metals, metal oxides, nitrides, doped semiconductors, etc. An effort is currently being made to implement plasmons in electric circuits, or in an electric circuit analog, to combine the size efficiency of electronics with the data capacity of photonic integrated circuits. Plasmonics can be understood as "light-on-metal-dielectric-interfaces," where electrons oscillate at the surface of a metal due to strong resonant interactions with the electric field of incident light. Due to the high scattering rate of electrons, ohmic losses in plasmonic signals are generally large, which limits the signal transfer distances to the sub-centimeter range, unless hybrid optoplasmonic light guiding networks, or plasmon gain amplification are used. Both surface plasmon polaritons propagating along the metal-dielectric interfaces and localized surface plasmon modes supported by metal nanoparticles are characterized by large momentum values, which enable strong resonant enhancement of the local density of photon states, and can be utilized to enhance weak optical effects of opto-electronic devices.
A nanophotonic resonator or nanocavity is an optical cavity which is on the order of tens to hundreds of nanometers in size. Optical cavities are a major component of all lasers, they are responsible for providing amplification of a light source via positive feedback, a process known as amplified spontaneous emission or ASE. Nanophotonic resonators offer inherently higher light energy confinement than ordinary cavities, which means stronger light-material interactions, and therefore lower lasing threshold provided the quality factor of the resonator is high. Nanophotonic resonators can be made with photonic crystals, silicon, diamond, or metals such as gold.
An Edge Emitting LED (ELED) fulfills the requirement of high brightness LED, which provides high efficiency coupling to optical fibers.
In light-emitting diode physics, the recombination of electrons and electron holes in a semiconductor produce light, a process called "electroluminescence". The wavelength of the light produced depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light. An LED is a long-lived light source, but certain mechanisms can cause slow loss of efficiency of the device or sudden failure. The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide, and others, with various trace doping elements, are used to produce different colors of light. Another type of LED uses a quantum dot which can have its properties and wavelength adjusted by its size. Light-emitting diodes are widely used in indicator and display functions, and white LEDs are displacing other technologies for general illumination purposes.
Michelle Povinelli is a Professor of Electrical Engineering and Physics and Astronomy at the University of Southern California and Fellow of the OSA and SPIE. In 2010 Povinelli was recognised among the "Innovators under 35" list in the MIT Technology Review magazine for predicting better photonic devices. In 2010 she was awarded a Presidential Early Career Awards for Scientists and Engineers.
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